Brake



May 21, 1935. PA E 2,001,937 BRAKE Fil ed May 17, 1950 s Sheets-Sheet 1l0 0/ 11/ v f I HUMPHREY F. PARKER A TTORNEY May 21, 1935. v H. F.PARKER 2,001,937

' BRAKE Filed May 17, 1930 s sheets-sheet 2 F/GJZ I INVENTOR;

HUMPHREY F. PARKER 'A TTORNEY May 21, 1935. I H;- F. PARKER 2,001,937

BRAKE v I I Filed May 17, 19:50 3 Sheets-Sheet a INVENT-OIIL HUMPHREY F.PARKER A TTORNEY Patented May 21, 1935 BRAKE Humphrey F. Parker, SouthBend, Ind., assignor to Bendix Brake Company, South Bend, hit,

a corporation of Illinois Application May 17, 1930, Serial No. 453,380

12 Claims.

This invention relates to brakes and more particularly to internalexpanding brakes.

In brakes of .the servo type, a thrust derived one primary shoe, forcingit in contact with di rect rotation of the drum. The heel of the primaryshoe is attached to the toe of the secondary shoe, forcing it in contactwith the drum, also in the direction of rotation with the drum.

This gives a greater increased braking effect but unfortunately it alsocauses variation in the co-eflicient of friction of the brake lining. Itis the aim of the present invention to improve this structure.

An object of the invention is areduction of the undesirable efiectswhich accompany changes in the co-eflicient of friction in brakes.

Another object of the invention is to improve the structure of brakes ofthe servo type which have a servo action'in both the forward and reversedirections.

Other objects will appear from the following description taken inconnection with the drawings and forming a part of this specification:

Figure l is a side elevation of a brake comprising two friction members.

Figure 2 is a section substantially on line 2--2, Figure l.

Figure 3 is a section substantially on line 3--3, Fi ure 1.

Figure 4 is a side elevation of a brake comprising three shoes to whichthe invention has been applied. Figure 5 is a section substantially online 5-5,

Figure 4.

Figure 6 is a section substantially on line 6-6, Figure 4.

Figure '7 is a, side elevation of a brake of the two-shoe type,illustrating a modification of the invention.

Figure 8 15a section substantially on line 8-8, Figure 7.

Figure 9 is a section substantially on line 9-9, Figure 7.

Figure 10 is a side elevation of a brake of a three-shoe type,illustrating an allocator of the invention.

Figure 11 is a section substantially on lin Ii--ll,Figure10. y

Figure 12 is a section substantially on line i2-I2, Figure 10.

' Figure 13 is a side elevation of a brake.comprising four shoes towhich the invention has been applied.

Figure 14 is a section substantially on line il-ll, Figure 13.

Figure 15 is a section substantially on line l5-I5, Figure 13.

Figure 16 is a side elevation of a brake comprising two shoes to whichthe invention has been applied.

Figure 17 is a section substantially on line 11-", Figure 16.

Figure 18 is a section substantially on line iii-l8, Figure 16.

Referring to the drawings for more specific details of the invention,Ill represents a rotatable drum at the open end of which is positioned afixed support such as a backing plate ll. Positioned for movement on thebacking plate is a primary shoe 1! and a secondary shoe I3. As shown,the primary shoe is mounted on anchors l4 and l5 and the secondary shoeis mounted on anchors i 6 and I1 and positioned between the shoes is acam l8.

The primary shoe is connected by a link- 20 to the anchor 16 and thesecondary shoe is connected by a link l9 to the anchor M. The link Ithas positioned thereon, a thrust roller 2i engaging the shoe l3 and thelink 20 carries a thrust roller 22 engaging the shoe II. The thrustrollers 2 land 22 engage the respective shoes substantially midway ofthe center of the shoe and the toe or shoulder end. Each shoe occupiessomewhat less than'half the circumference of the-brake drum. The. cam 18acts on the shouland the respective heels of the shoes are pinned tolinks which in turn are pinned to the anchors adjacent to the shoulders.

The links I! and 20 bear through the thrust rollers 2| and Hon theshoes, acting as levers with their fulcrums on the anchor pins I4 andIS. The reaction from the shoes is applied to the brake support at theanchor pins by a force greater than the reaction of the self-actuatingshoe as applied through the thrust rollers.

The heal of each shoe has a slot which flts over the anchor pins 15 andIf! located opposite .the cam. The heel of the self-actuating shoe 12moves away from the anchor, but the heel of the non-self-actuating shoeIt bears against it, so that the drag of the non-self-actuatingshoe isapplied to the brake support at this point. The link is of thenon-selbactuating shoe is inactive, making a slight rotary movementabout its anchor pin l4 andmoving away from the selfactuating shoe l2.When the direction of rotation of the wheel isyversing, theself-actuating shoe 82 becomes a non-seli-actuating shoe and vice versa.

' Figure 4 illustrates a three-shoe servo brake to which the inventionis applied. In this embodiment of the invention, the fixed support haspositioned thereon for movement, a primary shoe 23, a secondary shoe 2dand an auxiliary shoe 25. As shown, the secondary shoe 251s positionedon an anchor 26 and the auxiliary shoe is posttioned on an anchor 2i andan articulating pin 28 connects the primary shoe to a link, to behereinafter described. The primary shoe is and the auxiliary shoe 25 areprovided on their separable ends with rollers 29 and 3.0 between whichis positioned an operating cam 3!.

The primary shoe 2'3 and the auxiliary shoe 25 are connected by a coilspring 32 and the secondary shoe 24 is connected by a coil spring 33 toa fixed support on the backing plate. These springs serve to return theshoes to the off position and to retain them in proper spaced relationto the drum.

A link 34 is connected by one end to the articulating pin 28 and theother end of the link is pivoted on the anchor 21. This link carries athrust roller 35 adaptable for engagement with the secondary shoe 24 inspaced relation to the toe of the shoe. As shown, the thrust roller ispositioned midway between the center of the shoe and the toe. Whenthe'cam 3| is actuated, the toe of the primary shoe is applied to thedrum. This tends to move the shoe in the direction of rotation and does,in fact, do so slightly. The reaction of the forces acting on the shoeis applied to the link at the articulating pin 28 and through the link'38 connected thereto and to the anchor 21 and thrust roller 35 isforced against the secondary shoe to press the toe again the drum.

Figure 7 illustrates a modified form or the invention wherein the fixed.support or backing plate has positioned thereon a primary shoe 36 and asecondary shoe 31. As shown, the secondary shoe is positioned on ananchor 38 and the primary shoe is connected by a link 39 to an actuatingcam 40.

' The primary and secondary shoes are connected by a coil spring M andthe primary shoe is connected by a coil spring 42 to a fixed support 53.These springs serve toretu'rn the shoes to the ofi position and toretain them in proper spaced relation to the drum. The primary shoe ispivotally connected at its heel to a link 43 which in turn is pivotallyconnected to a link 44, anchored on the secondary shoe adjacent the toethereof, as indicated at 45.

The link 44 carries a thrust roller 46 in engagement with the secondaryshoe 3l. As the cam 40 is actuated to engage the toe oi the shoe 36 withthe drum, a slight movement of the shoes with the rotating drum isattained. This imparts a thrust through the link is and link 44 to theanchor 45, resulting in a radial force being applied to the shoe 3'!through the thrust roller #5. i t

Figure 10 embodies another modification oi the invention wherein thefixed support has positioned for movement thereon a primary shoe 41, asecondary shoe 48' and an auxiliary'shoe 49. The primary shoe 4'!and'the auxiliary shoe :49

have shoulder portions 50 and 60 between which acorns? auxiliary shoesare connected by a return spring and the secondary shoe is connected bya return spring 55 to a fixed support 66. The springs serve to returnand retain the shoes in the on position.

The secondary shoeis provided with a lug 61 engaging the link 62 andadapted to slide thereon.

When the cam is actuated to spread the primary and auxiliary shoes, thetoe of the primary shoe is moved to engage the drum, whereupon the shoemoves slightly with the drum. This causes a movement of the link 62 toimpart a radial force to the toe of the secondary shoe through lug Si orthrust roller, as the case may be. It is, of course, to be understoodthat when the direction of rotation of the drum is reversed, the actionof the primary and secondary shoe is also reversed.

Figure 13 illustrates a further modification of the invention, showingthe invention as applied to a four-shoe brake. In this embodiment of theinvention, the shoes are arranged in pairs, each pair comprising aprimary shoe 5B and a secondmy shoe 59, positioned on an anchor 10. Therespective pairs are mounted in oppositely disposed relation withrespect to each other. The primary shoes 88 have shoulders H and I2between which is positioned an operating cam 13.

The primary shoes are connected by a coil spring M and the secondaryshoes are connected by a coil spring l5. These springs serve to returnand retain the shoes in off position with a suitable clearance betweenthe shoes andthe drum.

Positioned on the backing plate and oppositely disposed with respect toeachother are studs 16 on which is mounted a cam I1. This cam isprovided with a thrust roller 18 and is adapted to be actuated by a link79 pivotally connected to the primary shoe $8 adjacent to the heelthereof.

In operation, when the cam is actuated to spread the shoes, the toes ofthe'primary shoe engage the drum and the shoe slightly rotatestherewith. This movement actuates a cam I! through the link 19 to directthe thrust roller 18 against the secondary shoe at a point removed fromthe toe thereof.

In Figure 16, I have illustrated a further modification form of theinvention. In this particular embodiment, the primary shoe 80 and thesecondary shoe 8| are positioned for movement on the backing plate Ii.As shown, the shoes are mounted on an anchor 82. The primary shoe isconnected by a link 83 to an actuating crank 84 and return springs 85and 36 are connected between the primary and secondary shoes and theprimary shoe and a fixed support to return and retain the shoes in theofi position with clearance between the shoes and the drum.

Connected between the primary shoe and the secondary shoe is a toggle 81upon which is positioned a thrust roller 88 in engagement with thesecondary shoe Bl. It should be noted that this toggle is connected atone end to the primary shoe adjacent the heel thereof and to thesecondmy shoe approximately midway of the center and toe of the shoe.The mode of operation of this particular structure is substantially thesame as that of Figure 7.

Although this invention has been described in connection with certainspecific embodiments, the principles involved are susceptible tonumerone other applications that will readily occur to personsskilled inthe art. The invention is, therefore, to be limited only as indicated bythe scope oi the appended claims.

Having thus described the various features of the invention, what Iclaim as new and desire to secure by Letters Patent is:

1. A brake comprising a fixed support, a plurality of friction elementspositioned for movement thereon, a drum associated with the frictionelements, means for actuating the friction elements for co-operationwith the drum, means connecting the toe of one friction element to theheel of the other friction element and means carried by the connectingmeans engaging the friction elements at a distance removed from the toesthereof to force the friction elements in engagement with the drum.

2. A brake comprising a fixed support, two friction elements positionedfor movement thereon, a lever connecting the toe of each frictionelement to the heel of the other friction element, thrust members on thelevers engaging the friction elements and means foractuating thefriction elements for engagement with the drum.

3. A brake comprising a fixed support, three friction elementspositioned for movement thereon, a drum associated with the frictionelements, anchors for at least two of the friction elements and a leverpivotally connected to the third friction element, a thrust rollercarried by the lever engaging one of the friction elements at a pointremoved from the toe thereof and means for spreading the frictionelements for uniform engagement with the drum.

4. A brake comprising a plurality of shoes, each pivoted at one end on alink extending beside the other shoe, and applying means acting on theother ends of said shoes.

5. A brake comprising a plurality of shoes, each mounted on anchoringmeans extending beside the other shoe for substantially its full lengthand anchored adjacent the opposite end of said other shoe.

6. A brake having a pair of shoes each having an anchor post adjacentone end, and means conmeeting the end of each shoe furthest from theadjacent post to the anchor post adjacent the end of the other shoe.

'7. A brake having a pair of shoes each havin an anchor post adjacentone end, and a link pivotally connecting the end of each shoe furthestfrom the adjacent post to the anchor post adjacent the end of the othershoe.

8. A brake having two shoes, an applying device acting on adjacent endsof the shoes, anchorage means adjacent the applying device, and meansconnected to the other end of each shoe and to the anchorage means andwhich extends past the other shoe.

9. A brake having two shoes, an applying device acting on adjacent endsof the shoes, anchorage means adjacent the applying device, and alinkage connected to the other end of each shoe and to the anchoragemeans and which linkage extends past the other shoe.

10. A brake comprising a shoe, an applying device engaging one end ofthe shoe, and a rigid link directly connected to the other end of theshoe at the side of the brake opposite the applying device and anchoredadjacent the applying device.

11. A brake comprising a shoe, an applying device engaging one end ofthe shoe, a linkage connected to the other end of the shoe and anchoredadjacent the applying device, and another shoe arranged beside thelinkage.

12. A brake comprising a shoe, an applying device engaging one end ofthe shoe,- a linkage anchoring the other end of the shoe, another shoearranged beside the linkage and operatively en- 'gaged by the linkage,and an anchor for the linkage arranged between the ends of said othershoe.

HUMPHREY F. PARKER.

